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SMACNA Class C Leakage Standards: 2026 Statutory Context
In the 2026 Malaysian HVAC landscape, SMACNA Class C Leakage Standards are defined by the allowable leakage rate in relation to duct surface area and static pressure.
However, under the Energy Efficiency and Conservation Act (EECA) 2024 and MS 1525:2024, utilizing only "Class C" sealing is now largely non-compliant for commercial office environments in Malaysia, as these regulations now mandate Seal Class A (sealing all seams, joints, and penetrations) to meet energy intensity targets.
1. The Engineering Definition of Leakage Class
The SMACNA formula for predicting leakage is based on the Leakage Class (
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$F$: Leakage rate (
$cfm/100\text{ ft}^2$). -
$P$: Static pressure (inches w.g.).
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$C_L$: Leakage Class.
In the SMACNA hierarchy, the expected Leakage Class for a duct depends on its Seal Class and its shape:
| Seal Class | Sealing Requirements | Rectangular CL | Round CL |
| Seal Class A | All Seams, Joints, & Penetrations | 4 | 2 |
| Seal Class B | All Joints & Seams | 8 | 4 |
| Seal Class C | Transverse Joints Only | 16 | 8 |
2. Statutory Conflict: Seal Class C vs. EECA 2024
Under the current 2026 enforcement of EECA 2024, "Class C" sealing is essentially obsolete for new commercial installations.
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The "Energy Waste" Mandate: EECA 2024 legally defines air leakage as "Spent Energy." To satisfy the Building Energy Intensity (BEI) targets, the Suruhanjaya Tenaga (ST) now requires a minimum of Seal Class A for all ductwork operating above 500 Pa.
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MS 1525:2024 Compliance: The latest Malaysian Standard has moved toward the ASHRAE 90.1-2025 alignment, specifying that all duct systems must be sealed to Class A to ensure the Specific Fan Power (SFP) remains below 1.6 kW/m³/s.
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Leakage Class 4: For rectangular ducts, the industry "Gold Standard" is now Leakage Class 4 (which requires Seal Class A), as this is the only way to ensure the VFD-driven AHU operates at its optimized frequency without fighting "false load" from leaks.
3. DW/143 "Class C" vs. SMACNA
It is critical for contractors in KL to distinguish between the two standards, as many 2026 specifications now use them interchangeably in error.
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SMACNA Seal Class C: The lowest level of sealing (Transverse joints only).
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DW/143 Class C: A high-performance standard for high-pressure systems (up to 2000 Pa).
If your project specifies "Class C," verify whether they mean the SMACNA construction seal (which is likely non-compliant) or the DW/143 performance class (which is a high-spec requirement).
4. The "Fire Mode" Statutory Protocol
Leakage standards are a life-safety issue under BOMBA (JBPM) 2026 regulations.
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Smoke Leakage: In a "Smoke Spill" event, a duct with only Class C sealing will allow toxic smoke to "break out" into ceiling voids, potentially bypassing fire compartments.
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BOMBA Audit: For a building to receive its annual Fire Certificate (FC), the smoke extraction ducts must pass a Duct Air Leakage Test (DALT) ensuring they meet the high-integrity Seal Class A requirements.
5. Why Partner with EKG (Malaysia) SDN BHD?
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Technical Integrity: We refuse to install "Seal Class C" systems for commercial clients because they fail the 2026 REA (Registered Energy Auditor) inspections.
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Precision Testing: We perform DALT on all EKG (Malaysia) SDN BHD installations to verify a Leakage Class 4 or better, ensuring your facility is ready for ST and BOMBA witness testing.
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GITA Compliance: Our Seal Class A installations are the technical prerequisite for claiming your 100% Green Investment Tax Allowance (GITA).
Is your ductwork leaking energy or failing to meet the 2026 Seal Class A mandate?
Contact EKG (Malaysia) SDN BHD today for a specialized Duct Air Leakage Test (DALT) & Statutory Audit.
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